Dr John Evans - B.Sc (Bristol) Ph.D. (Exeter) CPhys

MRI Research Fellow & MRI Lab Manager

Research summary

As the Chief Physicist of the Magnetic Resonance lab in CUBRIC, I am responsible for the optimisation of our 3 Tesla MR system for use as a tool for neuroimaging research, for example by the implementation of novel pulse sequences. This role also involves advising on experimental design and analysis across the whole range of MR methods – structural and functional imaging and spectroscopy.

My research interests include:

MR Spectroscopy

Evaluating the robustness of GABA measurement in vivo.

The optimisation of analysis methods for GABA spectra, and the development of a toolkit for the analysis of GABA data (Gannet)

TMS-MRI.

Working on hardware improvements to allow the integration of transcranial magnetic stimulation into the MR environment for simultaneous TMS and functional MRI.

Selected publications (2014 onwards)

Full list of publications

Media activities

As the School's Welsh language officer, and a fluent Welsh speaker, I am keen to bring neuroimaging to the public through the medium of Welsh. I have appeared on the following programmes to attempt to raise the profile of CUBRIC and the School of Psychology to a Welsh speaking audience:

“Mosgito”, BBC Cymru, September 2008. Appearance discussing how fMRI can be used to localise activity in the brain on Welsh-language magazine programme aimed at 12-15 year olds.

“Y Daith” (“The Journey”), S4C, November 2009. Appearance on the S4C programme discussing the effect of brain structure on an individual’s risk of alcoholism.

“The Brain: A Secret History”. BBC Four, January 2011. Appearance and filming support for the BBC Four programme documenting a research study investigating the effect of hallucinogenic drug psilocibin using functional MRI.

“I’r Eithaf” (“To the Extreme”), S4C, November 2011. Appearance on children’s TV programme running a set of functional MRI experiments on the show’s presenter, to discuss the how the brain processes.

Research topics and related papers

Repeatability of GABA Spectroscopy

There is a significant amount of research demonstrating that the inhibitory neurotransmitter γ-aminobutyric acid (GABA) is a useful biomarker for psychiatric disorders. Recently, work at the School of Psychology at Cardiff has demonstrated that the measurement of GABA concentration in the human brain is sufficiently sensitive to explain individual differences in a variety of behavioural tasks (e.g. Sumner et al, Nature Neuroscience, 2010, Boy et. al. Current Biology, 2010), and in personality traits (Boy et. al. Biological Psychiatry, 2011).

However, the measurement of neurotransmitters using edited MR spectroscopy is inherently insensitive, compared with imaging techniques.

For example, the concentration of GABA is approximately 50,000 times lower than the concentration of water, resulting in longer experiment times and larger voxel sizes than are achievable in imaging experiments. As a result, characterising the robustness of the experiment is very important, particularly as this can vary significantly between brain regions.

Gannet

As part of this research, I have been optimising the analysis method for GABA spectroscopy and, along with Richard Edden (Johns Hopkins University, Baltimore) we have incorporated this into a set of Matlab-based tools (the GABA Analysis Toolkit, "Gannet") which is currently being distributed to collaborating sites, prior to general release [link].